<?php

/**
 * @package php-font-lib
 * @link    http://php-font-lib.googlecode.com/
 * @author  Fabien M�nager <fabien.menager@gmail.com>
 * @license http://www.gnu.org/copyleft/lesser.html GNU Lesser General Public License
 * @version $Id: font_table_directory_entry.cls.php 38 2011-11-07 17:09:59Z fabien.menager $
 */

/**
 * Generic Font table directory entry.
 * 
 * @package php-font-lib
 */
class Font_Table_Directory_Entry extends Font_Binary_Stream {

    /**
     * @var Font_TrueType
     */
    protected $font;

    /**
     * @var Font_Table
     */
    protected $font_table;
    public $entryLength = 4;
    var $tag;
    var $checksum;
    var $offset;
    var $length;
    protected $origF;

    static function computeChecksum($data) {
        $len = strlen($data);
        $mod = $len % 4;

        if ($mod) {
            $data = str_pad($data, $len + (4 - $mod), "\0");
        }

        $len = strlen($data);

        $hi = 0x0000;
        $lo = 0x0000;

        for ($i = 0; $i < $len; $i += 4) {
            $hi += (ord($data[$i]) << 8) + ord($data[$i + 1]);
            $lo += (ord($data[$i + 2]) << 8) + ord($data[$i + 3]);
            $hi += $lo >> 16;
            $lo = $lo & 0xFFFF;
            $hi = $hi & 0xFFFF;
        }

        return ($hi << 8) + $lo;
    }

    function __construct(Font_TrueType $font) {
        $this->font = $font;
        $this->f = $font->f;
        $this->tag = $this->read(4);
    }

    function open($filename, $mode = self::modeRead) {
        // void
    }

    function setTable(Font_Table $font_table) {
        $this->font_table = $font_table;
    }

    function encode($entry_offset) {
        Font::d("\n==== $this->tag ====");
        //Font::d("Entry offset  = $entry_offset");

        $data = $this->font_table;
        $font = $this->font;

        $table_offset = $font->pos();
        $table_length = $data->encode();

        $font->seek($table_offset);
        $table_data = $font->read($table_length);

        $font->seek($entry_offset);

        $font->write($this->tag, 4);
        $font->writeUInt32(self::computeChecksum($table_data));
        $font->writeUInt32($table_offset);
        $font->writeUInt32($table_length);

        Font::d("Bytes written = $table_length");

        $font->seek($table_offset + $table_length);
    }

    /**
     * @return Font_TrueType
     */
    function getFont() {
        return $this->font;
    }

    function startRead() {
        $this->seek($this->offset);
    }

    function endRead() {
        //
    }

    function startWrite() {
        $this->seek($this->offset);
    }

    function endWrite() {
        //
    }

}

